Piston ring and method of making same



Umted States Patent l 13,545,775

[72] inventor Herbert F. Prune 2,970,023 1/1961 Thompson 277/2l6 Town and Country, Missouri FOREIGN PATENTS 1 pp 667374 664,114 1/1952 Great Britain 277/23sx [2 Filed July 24, 9 1,057,570 2/1967 Great Britain ..277/235(A)UX Division of Ser. No. 512,347, Dec. 8, 1965, Patent No. 3,421,198, which is a W s continuation oi Ser. No. 371,231, May 29, Amsmm Exlmmer jeffrey Medmck 1964! PatemNo 3,337,938, Aug 29,1967. Attorney-H1ll, Sherman, Merom, Gross & Slmpson I [45] Patented Dec. 8, 1970 [73] Assignee Ramsey Corporation St. Louis, Missouri 1 r a corporation ofOhlo ABSTRACT: A. unitary torsion-type compression ring in the form of a split annulus of a foundation metal having parallel upper and lower annular planar surface with a stepped [54] ig s z r OF MAKING SAME peripheral edge profile therebetween, the peripheral edge a g profile including a fillet intersecting the upper planar surface and terminating in a substantially planar annular radially ex- 2 /235 tending surface intermediate said upper and lower annular [51] ll. Cl. Fl6j 9/00 planar surfaces, a peripheral wall portion extending from said [50] Field ofSearch 277/ 139- intermediate planar annular surface toward but short of the l4l,2l6, 23l,223, 224, 234, 235,235(A), lower annular planar surface to leave exposed an annular (ATD); 29/ 156.4, 156.6, (ATD) i flange portion adjacent the lower annular planar surface, and a coating of a wear-resistant metal over said peripheral wall [56] References Cited portion so arranged and contoured as to provide a ring of un- UNITED STATES PATENTS balanced cross section with a peripheral annular flange por- 2,9os,s12 9/1959 Anderson 29/156.6x ,tion of the foundation metal projecting radially outwardly of 3,066,943 l2/l962 Brenneke 277/139 1 =1 the exposed surface of the wear-resistant metal- PISTON RING AND METHOD OF MAKING SAME This application is a division of application Ser. No. 512,347, filed Dec. 8, 1965, (now U.S. Pat. No. 3,42l,l98) dated .lan. I4, 1969 which, in turn was a continuation of my application Ser. No. 37l,23l,filed May 29, l964 and entitled Piston Ring and Method of Making Same, now US. Pat. No. 3,337,938, dated Aug. 29,1967.

The present invention is particularly directed to the manufacture of piston rings of the reverse torsion type consisting of a foundation metal, usually cast iron, and a hard metal coating bonded to the edge of the ring along selected areas thereof. This weanresistant metal, in the preferred embodiment of the invention, consists at least-predominately of molybdenum or tungsten, although other refractory metals having good hot hardness characteristics such as tantalum and osmium can also be used. The foundation metal of the ring provides a wearing in surface-for initial wiping or scraping contact with the wall of the cylinder in which the piston operates. Afterwards, the higher melting point and more resistant material of the coated areas comes into contact with the cylinder wall, thereby prolonging the useful life and service of the compression ring.

In my copending application Ser. No. 371,231 l have described an improved piston ring,=and a method for its manufacture involving placing the rings in multiples along an arbor with spacers between the individual pairs of rings. As the rings are rotated, they are grooved to provide upwardly radially inwardly inclined outer peripheral surfaces which are then filled with a higher melting metal.

The present invention provides an improvement over the aforementioned application particularly in the area of providing the grooves in the rings, and of the subsequent application of the hard metal therein. With the techniques of the present invention, the assembly of the rings on the arbor can be considerably simplified by the elimination of spacer rings, and the amount of grinding required to remove excess hard metal after application in the grooves is significantly reduced.

One of the objects of the present invention is to provide an improved method for simultaneously grooving a plurality of piston rings to produce a configuration of grooves in the rings which are designed for optimum disposition of hard metal therein.

Another object of the invention is to provide an improved method for the manufacture of piston rings faced with a hard metal deposit and providing an improved spraying technique for applying the hard metal to minimize the amount which has to be subsequently removed. 7

Another object of the invention is to provide a simple and relatively inexpensive method of manufacturing compression rings wherein the same fixturing used for providing the grooves in the edges of the ring is also used for the application of the sprayed-on metal.

Still another object of the invention is to provide an improved compression ring having a tapered, multifunction outer peripheral face and having an annular body of such cross section as to convert the ring into a torsion type of ring in service to thereby effect a better seal between the piston and the cylinder wall.

In general, the method of the present invention involves providing a plurality of rings of a foundation metal, each of the rings having a stepped profile providing shoulders along the edge of varying diameters. Identical rings of this configuration are positioned with their inner lateral surfaces in abutting coaxial alignment, thereby providing a plurality of grooves between the assembled rings. While the rings are rotated, they are sprayed with a molten wear-resistant metal directed at an angle to the axis of rotation to .thereby deposit the hard metal in preselected areas in the grooves while still permittingthe coated rings to be disassembled after the spraying operation.

Other objects and features of the present invention will become apparent to those skilled in the art from the following detailed description of the attached sheet of drawings in which:

FIG. 1 is a plan view of a split piston ring produced in accordance with the present invention;

FIG. 2 is a side elevational view of the ring shown in FIG. 1;

FIG. 3 is a greatly enlarged and somewhat exaggerated cross-sectional view taken substantially along the line llllll of FIG. I, and illustrates the deposit of hard metal along the edges of the ring;

FIG. 4 is a fragmentary view partly in cross section and partly in elevation of a fixture in which the rings are mounted in coaxial alignment; 7

FIG. 5 is a view similar to FIG. 4, but illustrating the first cutting operation which provides the grooves existing between the rings at their plane of abutment;

FIG. 6 is a view similar to FIG. 5, but illustrating a subsequent grooving operation wherein slightly tapered or straight grooves are provided in addition to the initial grooves shown in FIG. 5;

FIG. 7 is a view similar to FIG. 6, but illustrating rather schematically the metal-spraying operation by means of which the edges of the rings are provided with a hard metal coating;

FIG. 8 illustrates a subsequent grinding operation by means of which the excess metal is removed from the portions of the ring edge at which the foundation metal is to be exposed;

FIG. 9 is a view partially in elevation and partially in cross section illustrating a type of fixturing device used for aligning rings which have been pregrooved; and

FIG. 10 is a fragmentary view in perspective, and partially in cross section, illustrating a modified form of a piston ring which can be made with the process of the present invention.

Before proceeding with a specific description of the drawings, it should be noted that the configuration shown in the drawings are necessarily exaggerated somewhat to show the minute angles, the hard metal coating, and the like more clearly and to accomplish this objective, they must be shown in exaggerated form, as will be apparent to anyone skilled in the art.

As shown in the drawings:

In FIG. 1, reference numeral 12 has been applied generally to the piston ring of the present invention having a transverse part represented by a gap 13 which decreases to a narrow gap when the ring is installed on the piston. As best seen in FIG. 3 the ring is composed of a foundation metal body 14 having a stepped edge profile between'its upper planar surface 16 and its lower planar surface 17, the designation upper and lower" being in conformity with the position of those surfaces when they are in the groove in the piston and operating against the cylinder wall. The stepped edge profile includes a fillet l8 intersecting the upper planar annular surface 19. The edge profile of the ring also includes a wall 21 which merges through a fillet 22 with an annular flange portion 23 intersecting the lower planar surface 17. As illustrated in FIG. 3, the edge profile of the ring except for the annular flange portion 23 and a portion adjoining the upper planar surface 16 has a coating 24 of a hard, wear-resistant metal such as molybdenum. The coating may extend up along the surface 19, although it is not necessary that it do so.

As an indication of typical dimensions which can be used in the geometry shown in FIG. 3, the angle of taper designated at 26 is typically in the range from 1 to l/. The thickness of the annular flange portion 23 is measured in thousandths of an inch, typically from 0.005 to 0.015 inch. The radial distance from the inner edge of the fillet 18 to the outer periphery of the annular flange portion 23 may be on the order of 0.015 inch or so, while the maximum thickness of deposit of the coating metal 24 is usually less than 0.010 inch and may range fromabout 0.004 to 0.008 inch.

The initial step in the formation of the rings is shown in FIG. 4 of the drawings. In that FIG. reference numeral 31 indicates generally an arbor assembly comprising a rotatable shaft 32 secured to suitable drive means (not shown). Axially aligned along the shaft 32 are a plurality of plain rings 33 through 38 inclusive in tightly abutting alignment along the shaft 32. An end plate 39 cooperates with a similar end plate on the opposite side (not shown) to apply clamping pressure to the array of rings, the'pressure being supplied by means of a nut 41 in threaded engagement with the threaded end 42 on a shaft 32. A split sleeve 43 is positioned about the array of rings 33 to 38 to initially close and stack them in coaxial alignment. When suitableclamping pressure has been applied to the sides of the ring array, the sleeve 43 is removed.

With the rings 33 to 38 aligned as shown in FIGS. 4 and 5, the arbor 31 is rotated, and then grooves 44, 45 and 46 are out between the abutting planar surfaces of the pairs of rings by means of a cutting tool generally indicated at reference numeral 47 of the drawings. The particular tool shown in the drawings includes a plurality of spaced cutting tools 48, 49 and 50 for convenience, but it will be recognized that a single cutting tool can be used if desired. The medial plane of the cutting tools 48, 49 and 50 intersects the plane of abutment between the abutting rings, 33 and 34, for example, so that the axial'extent of the groove on both sides of the plane of abutment is equal.

Next, the edges of the rotating rings 33 to 38 are given a second grooving, to provide the tapered face 21 shown in FIG. 3 of the drawings. This is accomplished by providing a plurality of spaced cutting tools 52, 53 and 54 which groove the rings to provide slightly tapered wall portions 56, 57, 58, 59, 60 and 61 about the center grooves 44 to 46 inclusive as seen in FIG. 6. At the same time, the cutting tools leave peripheral lands, one of which is illustrated at reference numeral 62, the lands providing the exposed annular flange 23 of the finished ring as shown in FIG. 3 of the drawings.

Following the second grooving, the arbor 31 is put on a metal spray lathe for the reception of the hard metal coating in the grooves. This procedure has been somewhat schematically illustrated in FIG. 7 which illustrates a spray gun 64 directing a spray of molten metal (not shown) at an acute angle .to the axis of rotation. The angle referred to is measured in a clockwise direction from the axis of the shaft 32. The spray gun 64 is arranged to reciprocate during the rotation of the arbor 31 for spraying, and at the end of the travel of the spray gun 64 in one direction, the gun 64 is reinclined so that it prevents an obtuse spraying angle with respect to the axis of rotation, as illustrated in the dashed line showing of FIG. 7.

With the spray gun at an angle to the grooves, rather than nor- I ma] to the axis of the surface, the sprayed metal will not be projected to a substantial extent into the grooves 44, 45 and 46. The adjacent ring in each case shields the parting surface between the two adjacent rings so that little or no sprayed metal appears at the parting line between the adjacent rings. Alternatively, two spray guns can be used simultaneously, both at an angle to the axis of the arbor, provided their spray patterns do not intersect.

The operation of the spray gun 64 serves to provide a relatively thin hard metal coating generally identified at reference numeral 66 in the drawings. The coating will be somewhat thicker at the slightly tapered wall portions 56, 57, etc. and diminishes to substantially nothing at the base of the grooves 44, 45, etc.

The next operation is a grinding operation performed by a grinding wheel 67 to remove any hard metal coating which has become deposited on the peripheral lands 62. This step is illustrated in FIG. 8 of the drawings. Upon completion of this grinding operation, the individual rings may be removed from the arbor 31. Usually, further finishing operations are not necessary except possibly in certain applications where it may be desirable to lap the outer diameter surface for quick seating in the engine. 7

While the use of the same fixture for grooving and spraying forms the preferred embodiment of the present invention, it is also possible to perform the sprayingon rings which have been individually grooved. A suitable assembly is illustrated in FIG. 9, where the pregrooved rings are'identified at reference numeral 68 through 73, the rings being mounted coaxially with a shaft 74 by means of a centering sleeve 76. Axial pressureto the arr a of rings is provided by means of a plate 77, and a nut 78 whic 1s threadedly engaged on the threaded end of the shaft 74. Upon initial alignment of the pregrooved rings, the sleeve 76 is removed and then the spraying operation is carried out as shown in FIG. 7 of the drawings.

It is always necessary that the second grooving operation depicted in FIG. 6 provide a tapered wall for the edge profile. Actually, with no angle at all on this groove, there will still be a slight taper in the wall as illustrated in FIG. 3 of the drawings due to natural flow of the metal and a tendency ,to build up more on one side of the groove than the other.

A straight-faced-type of configuration can be made by the process of the present invention as illustrated in FIG. 10. There, reference numeral 81 indicates generally a piston ring composed of a foundation metal 82 having a substantially uniform thickness coating layer 83 of hard metal therealong. A pair of grooves 84 and 86 are provided at opposite end of the coated area. This type of structure can be made by inclining the spray gun 64 as mentioned previously to prevent direct impingement of the molten metal at the abutting face of the individual rings when the rings are coaxially aligned:

From the foregoing, it will be understood that the method of the present invention provides a simple but highly effective means for applying a hard metal coating on selected areas of a piston ring profile. The process is carried out with a minimum of fixtures, and with the necessity of less grinding to remove excess sprayed metal than processes heretofore employed for this purpose.

It should be evident that various modifications can be made to the described embodiments without departing from the scope of the present invention.

Iclaim:

1. A unitary split compression ring of the torsion type formed of a foundation metal annulus having parallel upper and lower annular planar surfaces with a stepped peripheral edge profile therebetweemsaid peripheral edge profile including a fillet intersecting the upper planar surface and terminating in a substantially planar annular radially extending surface intermediate said upper and lower annular planar surfaces, a

. peripheral wall portion extending from said intermediate planar annular surface toward but short of said lower annular planar surface to leave exposed an annular flange portion adjacent said lower annular surface, and a coating of a wear-resistant metal over said peripheral wall portion presenting an exposed surface tapered from said flange portion radially inwardly toward said fillet to overlie said intermediate annular surface but without filling said fillet, thereby providing a ring of unbalanced cross section with the foundation metal of said peripheral annular flange portion projecting radially outwardly of said exposed surface of said wear-resistant metal.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3,545 ,775 Dated December 8 1970 Herbert F. Prasse Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2 line 49 after "planar" insert surface 16 a terminating in a substantially planar Column 4 line 17 after "is" insert not line 54 after "annular" insert planar Signed and sealed this 21st day of December 1971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Pate 

